Introduction:Modern athletic performance is driven not only by physical capacity but also by rapid decision-making, attentional control, and visuomotor coordination. Evidence regarding the acute effects of caffeine (CAF), L-theanine (TEA), and their combination remains inconsistent, particularly with respect to their combined influence on physical and cognitive performance in athletic populations. This study examined the acute effects of isolated and combined CAF and TEA supplementation on maximal strength, intermittent aerobic endurance, and eye-hand coordination in competitive athletes. It was hypothesized that the combined ingestion of CAF and TEA would differentially affect physical performance and eye-hand coordination outcomes compared with isolated CAF or TEA intake. Methods:Twenty trained athletes completed four randomized, double-blind, placebo-controlled crossover conditions: CAF (3 mg·kg-1), TEA (200 mg), CAF+TEA (COM), and placebo (CON), with ≥72 h washout. Outcomes included isometric leg, back, and handgrip strength; Yo-Yo Intermittent Endurance Test Level 1 performance; and visuomotor coordination (CogniFit®). Data were analyzed using repeated-measures ANOVA with Bonferroni corrections (α = 0.05). Results:Condition effects were found for leg strength (p = 0.004, ηp2 = 0.24) and back strength (p = 0.008, ηp2 = 0.19). In the COM condition, no additional or synergistic effect on maximal strength was observed. Additionally, no significant difference was found between the conditions in aerobic endurance, maximum isometric handgrip strength, and hand-eye coordination results. Caffeine ingestion did not differ from placebo for any strength outcome under the present conditions. Finally, acute ingestion of TEA was associated with reduced maximal isometric leg and back strength compared with CAF and CON. Discussion:Findings challenge the prevailing assumption of CAF + TEA synergy and underscore the need for task-specific interpretation of co-supplementation strategies. Future studies should evaluate dose-response interactions, habitual caffeine intake, sex-specific responses, and broader cognitive domains beyond visuomotor control. The randomized controlled trial was registered at ClinicalTrials.gov, under the registration number NCT07268573. Clinical Trial Registration:ClinicalTrials.gov, NCT07268573.

BACKGROUND:Although caffeine is widely used in athletes due to its ergogenic effects, the effects of its main metabolite, paraxanthine, on performance and sleep have not been adequately investigated. PURPOSE:This study aimed to comparatively investigate the effects of caffeine and its main metabolite paraxanthine on rowing performance and sleep quality. METHODS:The study was designed as a randomized, double-blind, crossover study and included 14 male university-level rowers (21.6 ± 1.9 age; 2.2 ± 1 years of rowing experience). The participants participated in 2000-m rowing ergometer time trials under four different supplementation conditions (caffeine + paraxanthine, caffeine + placebo, paraxanthine + placebo, and placebo with 200  mg each). Performance data (completion time, mean power, and heart rate), sleep quality, and daytime sleepiness were assessed by subjective scales. The data were analyzed by repeated-measures analysis of variance (ANOVA) and Bonferroni post-hoc tests. RESULTS:Compared with the placebo, the combined caffeine + paraxanthine condition was associated with faster 2000-m performance and higher mean power output (p = 0.044; Cohen's d = 0.30). Caffeine alone and paraxanthine alone did not show clear evidence of performance improvement in this sample, although estimates favored both conditions versus placebo. Conditions containing caffeine were associated with poorer subjective sleep quality, whereas paraxanthine alone showed more favorable sleep-related outcomes. CONCLUSION:These results indicate that the combined ingestion of caffeine and paraxanthine elicited the most pronounced performance benefits, while paraxanthine alone did not demonstrate clear standalone ergogenic efficacy at the administered dose. However, paraxanthine was associated with better subjective sleep outcomes compared to caffeine, suggesting that its potential value may be related more to tolerability rather than superior performance enhancement, particularly for athletes training in the evening. Study limitations, including the small sample size and lack of objective sleep measures, should be considered when interpreting the results. PRACTICAL APPLICATIONS:Paraxanthine may represent a practical option for athletes who prioritize sleep quality or experience sensitivity to caffeine-related sleep disturbances, although further dose‒response studies are required to clarify its ergogenic potential.

Handball requires athletes to sustain intermittent high-intensity effort while maintaining rapid cognitive processing and technical skills. Caffeine is widely used as an ergogenic aid, yet its dose-dependent effects across physical, cognitive, and technical performance outcomes remain unclear in female handball players. This randomized, double-blind, placebo-controlled crossover study examined the acute effects of low-dose caffeine (LCAF; 3 mg/kg), moderate-dose caffeine (MCAF; 6 mg/kg), and placebo (PLA) in trained female handball players. Participants (n = 20) completed three experimental sessions separated by 72 h. Cognitive performance was assessed using the Simplified Eriksen Flanker Test, throwing performance was evaluated through maximal ball velocity, and intermittent running capacity was measured with the Yo-Yo Intermittent Recovery Test Level 1. Both LCAF and MCAF significantly improved Yo-Yo performance compared with PLA (η2p = 0.415, representing improvements of approximately ~23.5% and 29.0%), with no difference between caffeine doses. MCAF significantly reduced overall Flanker response time (η2p = 0.486, ~18.5%) and congruent and incongruent trial response time compared with PLA and LCAF. No significant effects were observed for throwing velocity, Flanker accuracy and interference scores. These findings suggest that acute caffeine intake has performance-specific effects in female handball players: intermittent running performance responded to both doses, whereas cognitive enhancement was limited to response time, with no improvements in inhibitory control or accuracy.

Sitting volleyball relies heavily on upper-body strength and anaerobic capacity. Serve, spike, and speed-endurance are decisive skills, yet the ergogenic potential of low-dose caffeine in this Paralympic sport remains unclear. To examine the acute effects of low-dose caffeine (3 mg/kg) supplementation on serve speed, spike speed, and speed-endurance in elite sitting volleyball players. Using a randomized, double-blind, crossover design, 13 elite male athletes from the Turkish National Sitting Volleyball Team completed serve speed, spike speed, and speed-endurance tests under caffeine (CAF) and placebo (PLA) conditions. Caffeine intake produced a moderate improvement in serve speed (p = 0.028, d = 0.460); however, this effect did not remain statistically significant after Bonferroni correction (adjusted p = 0.084). No significant effects were observed for spike speed (p = 0.547, d = 0.166) or speed-endurance performance (p = 0.709, d = 0.111). Perceived exertion during the speed-endurance test was similarly high in both conditions. Low-dose caffeine may offer a trend toward improved serve performance, but the effect was not robust after statistical adjustment, and no benefits were observed for spike speed or speed-endurance. These findings highlight that caffeine’s ergogenic effects are context-dependent and shaped by task complexity and sport-specific motor demands. Further research with larger and more diverse samples, genotype-based subgroups, and varied dosing strategies is warranted to clarify caffeine’s role in adaptive sports. The randomized controlled trial was retrospectively registered on 21/06/2025 at ClinicalTrials.gov, under the registration number NCT07056231.

IntroductionThis study investigated the dose-dependent effects of evening caffeine ingestion on rowing performance, sleep quality, and daytime sleepiness in trained male rowers.MethodsUsing a double-blind, randomized, crossover design, 13 university-level rowers (mean age = 22.07 ± 2.21 years; mean body mass = 77.66 ± 6.45 kg) completed four 2,000 m time–trial sessions between 19:00 and 20:00 h under placebo (PLA), low-dose capsule caffeine (3 mg/kg, LDC), moderate-dose capsule caffeine (6 mg/kg, MDC), and high-dose capsule caffeine (9 mg/kg, HDC) conditions. Performance metrics, heart rate, and subjective sleep assessments were collected. Rowing performance was assessed by a standard 2,000 m rowing ergometer (Concept II, United States) time trial. Sleep quality was measured with a numerical rating scale in the morning after each trial, and daytime sleepiness was measured with the Karolinska Sleepiness Scale.ResultsResults indicated significantly improved rowing times and power output with HDC and MDC compared to PLA (p < 0.05), with HDC yielding the most notable enhancements (d = 0.40–0.41). However, these ergogenic benefits were accompanied by significantly impaired sleep quality and elevated daytime sleepiness in both HDC and MDC groups (p < 0.01; d = 1.3–1.5). Notably, adverse effects such as headache, insomnia, and gastrointestinal discomfort were predominantly reported in the HDC condition (p < 0.05). Although LDC offered mild performance improvements with minimal sleep disruption, only the high dose condition exhibited large physiological and perceptual trade-offs.DiscussionThese findings indicate a clear dose–response relationship, wherein higher evening caffeine intake improves performance but has detrimental effects on sleep and recovery markers. Coaches and athletes should carefully balance caffeine dosing against potential recovery costs, especially in evening training or competition contexts.

The purpose of this study was to investigate the acute effect of low, moderate, or high doses of taurine on anaerobic and physiological performance in female rugby players. A total of 16 sub-elite female rugby athletes (21.3 ± 1.5 yr, 168.0 ± 4.9 cm, 62.1 ± 3.5 kg mean ± SD) participated in this research. Following familiarization, participants attended 4 successive tests separated by 72 h in a randomized, counter-balanced, crossover research design. Following an over night fast, participants completed a 5-min 60 Watt warm-up followed by a 30-s Wingate anaerobic test on a cycle ergometer after ingestion of either 2 g taurine (LOWTAU), 4 g (MODTAU), 6 g (HIGHTAU) or placebo (PLA) 1 h before the test. Peak (PP) and mean power (MP) along with heart rate (HR), rating of perceived exertion (RPE), capillary lactate and blood glucose were measured. LOWTAU did not affect PP, MP, HR, lactate and glucose compared to PLA (p > 0.05), while MODTAU improved MP and HIGHTAU improved PP and MP compared to PLA and LOWTAU (p < 0.05). MODTAU and HIGHTAU had little effect on HR, blood lactate and glucose (p > 0.05). A single dose of taurine (MODTAU or HIGHTAU) 1 h prior to competition or training would provide an ergogenic effect on subsequent power output.

Kafeinin fizyolojik ve psikolojik etkileri hususunda tüm sorular henüz yanıtlanamamıştır. Fakat sporcuların farklı fizyolojik belirteçler ve uyku kalitesine etkileri bilinmektedir. Bu çalışmada, futbolcularda aerobik kapasite ve algılanan uyku kalitesinde plasebo sakızının farklı dozları kullanıldığında oluşan değişikliklerin incelemesi amaçlanmıştır. Amatör futbol takımından 22 erkek oyuncunun (yaş:23,36 ± 5,4 yıl boy: 180,14 ± 6,9 cm; VA: 76,32 ± 10,2 kg; BKI: 23,51 ± 2,8 kg/m2) gönüllü olarak katıldığı araştırma rastgele, çapraz-döngülü, tek kör olarak planlanmıştır. 5 dakika çiğnemeleri istenilen plasebo sakızını çıkarttıktan hemen sonra futbolculara Yo-Yo Aralıklı Toparlanma Testi Seviye 1 (Yo-Yo IRT-1) uygulanmıştır. Katılımcılara her Yo-Yo IRT-1 denemesinden hemen sonra ‘’Sakız performansınızı nasıl etkiledi?’’ sorusu yöneltilmiştir. Her test gününden sonraki sabah tüm katılımcıların uykularında oluşabilecek değişikliklerin gözlenmesi için Richard-Campbell Uyku Ölçeği (RCSQ) ve Karolinska Uykululuk Ölçeği (KSS) uygulanmıştır. Aerobik kapasite ve uyku kalitesi verilerinde plasebo kullanıldığında istenilen yönde anlamlı bir farklılık görülmemiştir. Sonuç olarak, plasebo kafein amatör futbolcularda algılanan uyku kalitesinde ve aerobik kapasitede etkili olmamıştır.

Kafeinin (1, 3, 7, trimetilksantin) adenozin reseptörü üzerindeki antagonist etkisi, beta endorfin hormonunun salınımını, organizma içerisinde glikojenin mobilizasyonu ile yağ asitlerinin utilizasyonu performansını artırmaktadır. Ayrıca, sağladığı termojenik faydalar gibi etmenler sayesinde günümüzde sporcular arasındaki popülaritesi ile performans artırıcı bir ergojenik yardımcı olarak kullanımını ve her geçen gün artmaktadır. Günümüzde farklı formları olan kafeinin özellikle sakız formu sindirim sistemini elimine ederek direkt olarak yanak içi reseptörler aracılığı ile etki mekanizmasını devreye sokması nedeni ile diğer formlardan ayrılmaktadır. Bu çalışmanın amacı antrenmanlı sporcularda sakız formda akut kafein alımının dinamik denge parametresi üzerine bir etkisinin olup olmadığını araştırıp, elde edile verileri literatüre kazandırarak alana farklı bir bakış açısı kazandırmaktır. Tek kör çapraz döngülü kontrol gruplu tasarlanan çalışmaya 20 antrenmanlı erkek sporcu katılmıştır. Katılımcıların dinamik denge verileri Biodex Denge Sistemi (Biodex Medical Systems, Inc., Shirley, NY) içerisinde kayıtlı olan dokuz noktalı kararlılık sınırları protokolünün ikinci aşama zorluk seviyesi kullanılarak ölçülmüştür. Sonuçlar kafeinin sakızının bir nokta (ön sol) dışında antrenmanlı sporcularda dinamik denge performansını istatistiksel olarak anlamlılık oluşturacak seviyede geliştirmediği ancak birçok parametrede yükselen bir trend oluştuğunu göstermektedir.

Obesity is a global health problem that is increasing in prevalence and poses significant risks to the health of individuals. In recent years, bariatric surgery, especially sleeve gastrectomy, has become a widely adopted approach in the treatment of obesity. However, the role of post-operative physical activity, especially in women, has not been adequately studied. The aim of this study is to compare the body composition and blood lipid levels of adult obese women who do physical activity and those who do not for a year after bariatric surgery. Twenty-one women (PA group / non-PA group) participants with a sedentary lifestyle and a body mass index above 35 were included in the study. The PA group performed regular aerobic exercises, while the non-PA group maintained a sedentary lifestyle. Measurements were made in both groups preoperatively, at 1, 3, 6 and 12 months. The results showed that physical activity has a significant effect on body composition. Regarding blood lipid levels, physical activity contributed to significantly improvements in cholesterol, low-density lipoprotein and triglyceride levels over the 12-month period. However, no significant relationship was found between physical activity and high-density lipoprotein levels. In summary, this study highlights the beneficial effects of physical activity on body composition and some blood lipid parameters in women after sleeve gastrectomy.

Handball is a high-intensity team sport requiring muscle power and high aerobic capacity. Caffeine is a commonly used ergogenic aid known to enhance sports performance. However, its effects on female handball players remain unclear. This study aims to investigate the effects of acute low (LCAF) and moderate (MCAF) doses of caffeine intake on aerobic endurance and throwing velocity in trained female handball players. Fifteen trained female handball players participated in this randomized, double-blind, crossover study. Participants completed four sessions, including a familiarization session and three test sessions. The test sessions involved ingesting either 3 mg/kg (LCAF) or 6 mg/kg (MCAF) of caffeine or a placebo (PLA). Throwing velocity and aerobic endurance were measured using a hand radar gun and the Yo-Yo Intermittent Recovery Test Level 1, respectively. The results showed a significant improvement in aerobic endurance with both LCAF and MCAF doses of caffeine compared to the PLA condition (f= 5,993; p= ,014; η2= ,480). However, there was no significant difference in throwing velocity between the caffeine and placebo conditions (f= ,040; p= ,961; η2= ,006). Acute LCAF and MCAF doses of caffeine supplementation can enhance aerobic endurance but do not affect throwing velocity in trained female handball players. These findings contribute to the limited literature on the effects of caffeine in trained female handball players and suggest that caffeine may be a useful nutritional strategy for improving performance in this sport.

The ergogenic benefits of caffeine have been well established, but there is scarce research on its chewing gum form. The present research aimed to examine the effects of different doses (100 and 200 mg) of caffeinated chewing gum on muscle strength, vertical jump performance, and ball-kicking speed in trained male soccer players. In a double-blind, randomized counterbalanced, and crossover research design, 14 male soccer players (age = 22 ± 2 y; body mass = 74.2 ± 7.1 kg; height = 180.0 ± 6.8 cm; habitual caffeine intake = 358.9 ± 292.4 mg/day) participated in three experimental trials. In each trial, participants performed isometric handgrip strength, quadriceps and hamstring strength, ball-kicking speed, and 15 s countermovement jump test 10 min after chewing 100 mg (LCAF) or 200 mg (MCAF) of caffeinated gum or placebo (PLA). MCAF improved quadriceps strength (53.77 ± 5.77 kg) compared to LCAF (49.62 ± 8.81 kg, p = 0.048) and PLA (49.20 ± 7.20 kg, p = 0.032). However, neither LCAF nor MCAF had a significant effect on the isometric handgrip and hamstring strength, ball-kicking speed, and 15 s countermovement jump test (all p > 0.05). These findings support chewing gum as an alternative mode of caffeine administration which can be used as a nutritional ergogenic aid for trained soccer players, at least for quadriceps strength.

Caffeine mouth rinsing (CMR) has been shown to enhance exercise performance. However, no studies have analyzed the effects of different dosages of CMR on muscular performance. Therefore, the purpose of this study was to examine the effects of different dosages of CMR on strength (bench press 1 repetition maximum (1-RM)) and muscular endurance (60% of 1-RM repetitions to failure) in resistance-trained males. Fourteen resistance-trained males (age: 23 ± 2 years, height: 179 ± 3 cm, body mass: 83 ± 4 kg, BMI: 17 ± 2 kg/m2) completed four conditions in random order. The four conditions consisted of a mouth rinse with 25 mL solutions containing either 1% (250 mg) of CMR (low dose of CMR: LCMR), 2% (500 mg) of CMR (moderate dose of CMR: MCMR), 3% (750 mg) of CMR (high dose of CMR: HCMR) and sweetened water (placebo: PLA) for 5 s prior to a bench press strength and muscular endurance test. Maximal strength, muscular endurance, heart rate (HR) and ratings of perceived exertion (RPE) were recorded for each condition. There were no significant differences in strength (p = 0.30) and HR (p = 0.83) between conditions. HCMR significantly increased muscular endurance performance (p = 0.01) and decreased RPE values (p = 0.01). In conclusion, CMR did not affect bench press 1-RM strength performance, but muscular endurance responses to CMR seems to be dose-dependent.

The purpose of this research was to examine the effect of rinsing of carbohydrate in the mouth on bench press strength and endurance performance in resistance-trained athletes. 15 men (Age: 21.6 +/- 1,3 years, Height: 181.2 +/- 10,0 cm, Body Weight: 83.3 +/- 14.4 kg), who performed upper-body resistance training at least 5 days a week for the last 1 year, participated in this research. After the familiarization test day, participants took part in a total of 2 test days with a randomized, counterbalanced, crossover study design: 6% (1.5 gr) weight / volume (w/v) carbohydrate mouth rinsing (cho) with 25 ml water or mouth rinse with water (PLA). After a 10-hour night fasting, with olympic barbell bar, one repetition maximum (1RM) of participants was determined to evaluate upper body strength, immediately before 1RM attempt participants rinsed the solution. Muscular endurance was measured by lifting 40% of 1RM until exhaustion in 3 sets. 3 min of passive rest was allowed between sets and at the beginning of each minute mouth rinsing was applied. During the test protocol heart rate (HR), lactate (LA), glucose (GL), arousal (AR) and ratings of perceived exertion (RPE) were measured. Paired Samples T-test and two-way repeated measures ANOVA were used for data analysis. No significant differences were detected between the trials in the values of upper-body strength (p=0.43), muscular endurance (for repetition number, p=0.57; for total kg, p=0.43), HR (p=0.71), LA (p=0.42), GL (p=0.36), AR (p=0.19) and RPE (p=0.51).

Carbohydrate (CHO) mouth rinse has been shown to enhance aerobic endurance performance. However, the effects of CHO mouth rinse on muscular strength and endurance are mixed and may be dependent on dosage of CHO. The primary purpose was to examine the effects of different dosages of CHO rinse on strength (bench press 1 repetition maximum [1-RM]) and muscular endurance (40% of 1-RM repetitions to failure) in female athletes. Sixteen resistance-trained females (age: 20 ± 1 years; height: 167 ± 3 cm; body mass: 67 ± 4 kg; BMI: 17 ± 2 kg/m2; resistance training experience: 2 ± 1 years) completed four conditions in random order. The four conditions consisted of a mouth rinse with 25 mL solutions containing either 6% of CHO (Low dose of CHO: LCHO), 12% CHO (Moderate dose of CHO: MCHO), 18% CHO (High dose of CHO: HCHO) or water (Placebo: PLA) for 10 s prior to a bench press strength and muscular endurance test. Maximal strength (1-RM), muscular endurance (reps and total volume), heart rate (HR), ratings of perceived exertion (RPE) and glucose (GLU) were recorded each condition. There were no significant differences in strength (p = 0.95) or muscular endurance (total repetitions: p = 0.06; total volume: p = 0.20) between conditions. Similarly, HR (p = 0.69), RPE (p = 0.09) and GLU (p = 0.92) did not differ between conditions. In conclusion, various doses of CHO mouth rinse (6%, 12% and 18%) have no effect on upper body muscular strength or muscular endurance in female athletes.

In this study, it was aimed to examine the body composition, anthropometric and strength parameters of level cadet male cyclists at the national team level and to evaluate the relationship between the body composition, anthropometric and strength parameters. A total of 28 cadet male cyclists (age: 14.92±0.76, height:170,52±5.54, weight:60.47±5.59) participated in the study. Anthropometric characteristics of the subjects; height, body weight, body fat percentage, body mass index, skinfold thickness were measured, body fat percentage was determined using the “Yuhasz” formula, and motoric characteristics such as right and left handgrip strength, back strength and leg strength were measured. The analysis of the data was made in the SPSS statistical program and evaluated with the Pearson Correlation test. The result of the study, body fat percentage (8.949±1,104) and body mass index (20,786±1.555) were found. It was determined that the right handgrip strength (42,553±5,862), left handgrip strength (40.535±5,864), back strength (119,839±15,442) and leg strength (134,125±21,833) of the cadet cyclists were found. In addition, when the difference between handgrip strengths of the cyclists was examined, it was seen that the right hand was dominant. While there was a significant and positive correlation between body weight and right & left handgrip strength and back strength (r=0.478, p=0.01; r=0.405, p=0.032; r=0.409, p=0.031); it was determined that there was no correlation between body weight and leg strength (p>0.05). In addition, while there was an average significant and positive correlation was found between body mass index and only right handgrip strength (r=0.417, p=0.027), it was found that there was no significant correlation between age, height, fat ratio and strength parameters (p>0.05). As a result; this study showed that cadet cyclists have good hand grip, back and leg strength, and there is a significant correlation only between body weight and handgrip strength values, among the anthropometric characteristics. However, it was determined that there was no significant correlation between and anthropometric characteristics and leg strength, which is important for cyclists.

Previous studies have investigated caffeine (CAF) and taurine (TAU) in isolation and combined during exercise in males. However, the potential synergistic effect during high-intensity exercise remains unknown in female athletes. Seventeen female team-sport athletes participated (age: 23.4 ± 2.1 years; height: 1.68 ± 0.05 m; body mass: 59.5 ± 2.2 kg). All participants were habitual caffeine consumers (340.1 ± 28.6 mg/day). A double-blind randomized crossover design was used. Participants completed four experimental trials: (i) CAF and TAU (6 mg/kg body mass of CAF + 1 g of TAU), (ii) CAF alone; (iii) TAU alone; and (iv) placebo (PLA). Supplements were ingested 60 min before a 30-s Wingate Anaerobic Test (WAnT). Heart rate and blood lactate (BL) were measured before and immediately after the WAnT; and ratings of perceived exertion (RPE) were recorded immediately after the WAnT. Peak power (PP) was significantly higher following co-ingestion of CAF+TAU compared to PLA (p = 0.03) and TAU (p = 0.03). Mean power (MP) was significantly higher following co-ingestion of CAF+TAU compared to PLA (p = 0.01). No other differences were found between conditions for PP and MP (p > 0.05). There were also no observed differences in fatigue index (FI), BL; heart rate; and RPE between conditions (p > 0.05). In conclusion, compared to PLA the combined ingestion of 6 mg/kg of CAF and 1 g of TAU improved both PP and MP in female athletes habituated to caffeine; however; CAF and TAU independently failed to augment WAnT performance.